Data connection unexpectedly closed using WinSCP.com

Data connection unexpectedly closed using WinSCP.com

We are experiencing an intermittent failure using WinSCP.com (version 5.7.5) while trying uploads to a remote server. The behavior is not predictable but happens consistently when it happens. Here is a current example:

Update - problem resolved but still have a question

We were able to address the issue by adding the "-explicit" switch to the end of the commands in the open section. We then added this to our NAnt build scripts - along with the creation of the necessary certificates in the WinSCP.ini file - and thankfully our builds are no longer failing (which is very awesome).

The question that remains is why does this only happen very rarely and only with certain files? Size/naming convention/location do not seem to be relevant variables and 95% of the time, everything is fine. Only on rare occasions do we need explicit mode enabled and the challenge for a certificate using TLS. Any thoughts around that?